Plating solution for thick copper electroplating of ceramic substrate and use method of plating solution

Abstract

The invention provides an electroplating solution for thick copper electroplating of a ceramic substrate. The electroplating solution comprises copper sulfate pentahydrate, sulfuric acid and hydrochloric acid, and an additive system comprises a first type of additive, a second type of additive and a third type of additive; the first type of additive is a mixture of one or more of polyethylene glycol, polypropylene glycol, ethylene oxide and a block copolymer, and the second type of additive is a mixture of one or more of sodium dithiodipropane sulfonate, 3-mercapto-1-sodium propane sulfonate, phenyl sodium dithiodipropane sulfonate and 2-mercaptobenzimidazole. When the ceramic substrate thick copper electroplating solution is applied to ceramic substrate thick copper electroplating, a high-quality coating is obtained, meanwhile, the average thickness difference of the coating can be controlled to be smaller than 10 micrometers, the thickness difference of the coating can be controlled to be smaller than 10 micrometers, and the thickness difference of the coating can be controlled to be smaller than 10 micrometers. Wherein the control capability of the thickness of the copper layer is in a leading position in similar inventions and existing production technologies.

Description

Technical Field

[0001] The present invention belongs to the technical field of additives for thick copper electroplating on ceramic substrates, and particularly relates to an electroplating solution for thick copper electroplating on ceramic substrates and a method for using the same. Background Art

[0002] Ceramic substrates are an indispensable part of electronic packaging, mainly made of ceramic materials such as alumina and aluminum nitride, and have excellent properties such as high thermal conductivity, high insulation, high mechanical strength, high chemical stability, and low thermal expansion coefficient. They are widely used in the packaging of electronic components such as integrated circuits, hybrid integrated circuits, and power circuits, effectively improving the stability and reliability of electronic components. With the increasing requirement for the planarization of chip packaging, higher requirements are put forward for the thickness uniformity of the metal layer of ceramic substrates, and a representative one is the demand for high-quality thick copper electroplating.

[0003] During the electroplating process, additives play a crucial role. The first type of additives such as polyethylene glycol can inhibit hydrogen evolution on the surface and reduce surface defects; the second type of additives such as sodium polydithiopropane sulfonate mainly adsorb in areas with low mass transfer rate and low current density, and at the same time can accelerate the deposition of copper and reduce the influence brought by the edge effect; the third type of additives such as nitro blue tetrazolium chloride mainly adsorb in areas with high current density, reduce the copper deposition rate at the microscopic tip, and finally achieve high-quality thick copper electroplating on ceramic substrates.

[0004] At present, the research on the electroplating performance and principle of thick copper on ceramic substrates is not sufficient. Therefore, the research and development of the three types of additives for copper electroplating on ceramic substrates contribute to the development and progress of the ceramic substrate industry.

[0005] In the thick copper electroplating process of ceramic substrates, after the thick copper electroplating is completed, the thickness difference of the copper layer is often too large due to the edge effect; and due to the uneven growth of grains, the uniformity of the copper layer is poor, the grains are thick and the surface is rough. As Figure 1 shown in the cross-sectional view of the current thick copper electroplating of ceramic substrates of a certain company, the thickness difference of the copper layer is 20μm after copper electroplating. This thickness difference can be further reduced by the interaction of the three types of additives in the copper electroplating solution, which is beneficial to the subsequent chemical mechanical polishing.

[0006] In the Chinese patent with the publication number CN119243271A and the title "Electroplating Copper Plating Solution for Filling X-shaped Holes in Printed Circuits and Its Application", an electroplating copper plating solution for filling X-shaped holes in printed circuits is disclosed. The plating solution includes copper sulfate pentahydrate, sulfuric acid, and sodium chloride, and the additive system includes a first type of additive, a second type of additive, and a third type of additive; the first type of additive is one or more of polyethylene glycol, polypropylene glycol, block copolymer of ethylene oxide and propylene oxide, etc., the second type of additive is one or more of sodium polydithiopropane sulfonate, sodium 3-mercapto-1-propane sulfonate, sodium phenyl polydithiopropane sulfonate, 2-mercaptobenzimidazole, etc., the third type of additive is one or more of 1-methyl-4-nitroimidazole, azathioprine, 6-mercaptopurine, 2-thioxanthine, etc. This invention is applied to X-shaped hole filling and has a high-quality filling effect, with the average increase in surface copper controlled to be less than 13μm and the depression degree less than 4μm. The plating solution scheme disclosed by this invention has a certain representativeness.

[0007] For the above reasons, the present invention proposes an additive system that can be applied to high-quality thick copper electroplating on ceramic substrates and can meet the actual requirements in printed circuit manufacturing. Summary of the Invention

[0008] The purpose of the present invention is to provide an electroplating solution and its application for thick copper electroplating on ceramic substrates.

[0009] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0010] An electroplating solution for thick copper electroplating on ceramic substrates, the preparation raw materials of the electroplating solution at least include 180g / L - 250g / L of copper sulfate pentahydrate, 50g / L - 120g / L of sulfuric acid, and 50mg / L - 80mg / L of hydrochloric acid (calculated as HCl), as well as a first type of additive, a second type of additive, and a third type of additive;

[0011] The first type of additive is a non-ionic surfactant, at least including one or more mixtures of polyethylene glycol, polypropylene glycol, sorbitan ester, polysorbate, or block copolymer. The concentration of the first type of additive in the electroplating solution is 300mg / L - 500mg / L;

[0012] The second type of additive is a sulfonate anionic surfactant; the concentration of the second type of additive in the electroplating solution is 10mg / L - 30mg / L;

[0013] The third type of additive is selected from small molecule or polymer molecules of dyes or organic amines that can adjust the crystal grain structure of electroplated copper during electroplating, play a polarization role in the electrodeposition process, and make the electroplating rate at the micro-peaks on the material surface less than that at the micro-valleys.

[0014] Preferably, the sulfonate anionic surfactant includes at least one or a mixture of several of sodium polydithiopropane sulfonate, sodium dodecylbenzenesulfonate, 3-mercapto-1-propanesulfonate, and phenyl polydithiopropane sulfonate.

[0015] Preferably, the third type of additive is one or several of nitro blue tetrazolium chloride, thiazolyl blue, and acridine flavine.

[0016] Preferably, the third type of additive is used in combination with thiazolyl blue and acridine flavine.

[0017] Preferably, the dosage of thiazolyl blue and acridine flavine in the electroplating solution is 1:0.1 - 0.5.

[0018] Preferably, the concentration of the third type of additive in the electroplating solution is 1 mg / L - 10 mg / L.

[0019] Preferably, the concentration of the third type of additive in the electroplating solution is 3 mg / L - 8 mg / L.

[0020] Preferably, the ceramic substrate is an aluminum nitride ceramic substrate.

[0021] A method for using the electroplating solution according to claim 1, at least including the following steps:

[0022] S1. Degrease, micro-etch, and pre-dip the ceramic substrate;

[0023] S2. Pour the prepared plating solution into the plating bath, use the ceramic substrate treated in S1 as the cathode, use soluble phosphor copper as the anode, and perform electroplating with a DC power supply. Among them, the current density is 0.5 A / dm 2 ~2 A / dm 2 , the plating solution temperature is 22 ± 3 °C, and the electroplating time is 400 - 900 min.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] The electroplating copper plating solution additive system for thick copper electroplating of a ceramic substrate provided by the present invention has a simple molecular structure and good effects for the third type of additive used; applying the plating solution additive system provided by the present invention on a ceramic substrate, while obtaining a high-quality coating, the average thickness difference of the surface copper is controlled to be less than 10 μm, and the control ability of the average thickness difference of the surface copper is in the leading position among similar inventions and existing production technologies. At the same time, the obtained copper surface is flat and bright, which can meet the needs of industrial production. Description of the Drawings

[0026] Figure 1 It is the metallographic diagram of thick copper electroplating of a certain company in the market currently;

[0027] Figure 2 The metallographic diagram of the thick copper electroplating obtained in Example 1;

[0028] Figure 3 The metallographic diagram of the thick copper electroplating obtained in Example 2; Detailed implementation manners

[0029] The following uses specific specific examples to illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0030] The example provides an electroplating solution for thick copper electroplating of a ceramic substrate. The preparation raw materials of the electroplating solution at least include 180 g / L - 250 g / L of copper sulfate pentahydrate, 50 g / L - 120 g / L of sulfuric acid, and 50 mg / L - 80 mg / L of hydrochloric acid (in terms of HCl, the actual chloride ion concentration should be 50 mg / L - 80 mg / L), as well as a first type of additive, a second type of additive, and a third type of additive;

[0031] The first type of additive is a non-ionic surfactant that can inhibit copper deposition, and at least includes one or several mixtures of polyethylene glycol, polypropylene glycol, sorbitan ester, polysorbate, or block copolymer. The concentration of the first type of additive in the electroplating solution is 300 mg / L - 500 mg / L;

[0032] The second type of additive is a sulfonate anionic surfactant that can accelerate copper deposition and make the copper surface bright, effectively improving the flatness of the electroplating layer; the concentration of the second type of additive in the electroplating solution is 10 mg / L - 30 mg / L;

[0033] The third type of additive is selected to be able to adjust the crystal grain structure of electroplated copper during electroplating, play a polarization role in the electrodeposition process, and make the electroplating rate at the micro-peaks on the material surface less than that at the micro-valleys for small molecule or polymer molecules of dye type or organic amine type. The role of the third type of additive is to quickly adsorb onto the surface of the electroplated part and preferentially cover the micro-peak area, play a polarization role in the electrodeposition process, so that the electroplating rate at the micro-peaks is less than that at the micro-valleys, thereby effectively improving the flatness of the electroplating layer. In addition, the third type of additive can also adjust the crystal grain structure of electroplated copper to make it more uniform and fine, further improving the microscopic structure and performance of the electroplating layer. At the same time, the addition of the third type of additive enhances the adhesion between the electroplating layer and the substrate, prevents the occurrence of hydrogen embrittlement, and makes the electroplating process more flexible and controllable, capable of adapting to electroplated parts of different materials, thicknesses, and requirements. During the electroplating of copper, the reasonable use of the third type of additive is of great significance for improving the electroplating quality and efficiency.

[0034] The sulfonate anionic surfactant includes at least one or a mixture of several of sodium polydithiopropane sulfonate, sodium dodecylbenzenesulfonate, 3-mercapto-1-propanesulfonate, and phenylpolydithiopropane sulfonate.

[0035] The third type of additive is one or several of nitro blue tetrazolium chloride, thiazolyl blue, and acridine flavine.

[0036] The third type of additive uses thiazolyl blue and acridine flavine in combination.

[0037] The dosage of thiazolyl blue and acridine flavine in the electroplating solution is 1:0.1 - 0.5.

[0038] The concentration of the third type of additive in the electroplating solution is 3mg / L - 8mg / L.

[0039] The following is illustrated by examples:

[0040] Taking the third type of additive as a single variable: Using an aluminum nitride ceramic substrate, in the basic electroplating solution: copper sulfate pentahydrate with a concentration of 200g / L, concentrated sulfuric acid with a concentration of 90g / L, and hydrochloric acid (calculated as HCl) with a concentration of 70mg / L;

[0041] Using an ethylene oxide and propylene oxide block copolymer as the first type of additive, with a concentration of 400mg / L;

[0042] Using sodium polydithiopropane sulfonate as the second type of additive, with a concentration of 30mg / L;

[0043] The usage method of the electroplating solution includes the following steps:

[0044] Step 1. Pretreat the ceramic substrate, including degreasing, micro-etching, and pre-impregnation;

[0045] 1.1 Degreasing:

[0046] The degreasing solution consists of 20g / L of sodium hydroxide, 1g / L of sodium dodecylbenzenesulfonate, 3g / L of sodium carbonate, 5g / L of trisodium phosphate dodecahydrate, and deionized water. Then immerse the ceramic substrate in the degreasing solution and process for 5 minutes;

[0047] 1.2 Micro-etching:

[0048] The micro-etching solution consists of sulfuric acid with a mass fraction of 5%, sodium persulfate with a mass fraction of 5%, and deionized water. Then immerse the ceramic substrate obtained after the treatment in step 1.1 in the micro-etching solution and process for 30 seconds;

[0049] 1.3 Pre-impregnation:

[0050] The pre - dipping solution consists of sulfuric acid with a mass fraction of 5% and deionized water. Then, the ceramic substrate obtained after the treatment in Step 2.2 is immersed in the pre - dipping solution for 5 minutes.

[0051] Step 2: Thick copper electroplating of the ceramic substrate:

[0052] Pour the plating solution prepared in Step 1 into the plating bath. The ceramic substrate after the pretreatment in Step 2 is directly placed and fixed in the middle of the plating bath as the cathode, and soluble phosphor - copper is used as the anode plate on both sides. DC power is used for electroplating. Among them, the current density is 1 A / dm 2 , the temperature of the plating solution is 22 ± 3 °C, the air stirring speed is 1 L / min, and the electroplating time is 600 minutes.

[0053] The electroplated ceramic substrate obtained in Step 2 is washed with water and then dried. After making slices, it is observed and photographed under a metallurgical microscope. Measure the surface copper thickness, where the surface copper thickness refers to the thickness from the surface copper to the magnetron - sputtered seed layer.

[0054] We use the concentration or composition of the third - type additive as a single variable for testing:

[0055] Example 1:

[0056] Nitro - blue tetrazolium chloride is used as the third - type additive, and the concentration is 18 mg / L.

[0057] Example 2:

[0058] Nitro - blue tetrazolium chloride is used as the third - type additive, and the concentration is 6 mg / L.

[0059] The ceramic substrates obtained in Example 1 and Example 2 are made into slices and then observed and photographed under a metallurgical microscope, corresponding to Figure 2 and Figure 3 . Measure the surface copper thickness, where the surface copper thickness refers to the thickness from the surface copper to the magnetron - sputtered seed layer.

[0060] Figure 2 Figure is the longitudinal sectional view of the ceramic substrate observed by a metallurgical microscope after thick copper electroplating of the ceramic substrate in Example 1; the measurement results show that the difference in the surface copper thickness of the ceramic substrate obtained by using this formula exceeds 20 μm. The difference in the surface copper thickness of the ceramic substrate obtained by using this formula is too high. After analysis, it is considered that it is caused by the relatively high content of the third - type additive, resulting in slower copper growth in the middle position far from the boundary. After appropriately reducing the concentration of the third - type additive (such as 3 mg / L - 8 mg / L), it has a better performance in the difference of surface copper thickness.

[0061] Example 3:

[0062] Thiazolyl blue and acridine flavine are used as the third type of additive, and the dosage ratio is thiazolyl blue: acridine flavine = 1:0.2; the concentration of the third type of additive is 6 mg / L. The slices prepared from the electroplating solutions of Examples 2 and 3 were observed under a metallurgical microscope multiple times and compared. It was found that the average difference in the surface copper thickness of the ceramic substrates prepared with the third type of additive in a specific ratio of thiazolyl blue: acridine flavine was 10%-20% smaller than that with only nitro blue tetrazolium chloride at the same concentration. We believe that the third type of additive with a specific ratio of thiazolyl blue: acridine flavine can better balance the copper growth rates at the edges and the middle of the substrate, thus having a better performance in the difference of surface copper thickness.

[0063] The above embodiments are preferred implementation methods of the present invention for illustrating the present invention. However, the present invention is not limited to the specific details in the above embodiments. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can be made, and these all belong to the protection scope of the present invention.

[0064] The above embodiments are only illustrative of the principles and effects of the present invention and are not used to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. An electroplating solution for thick copper electroplating on a ceramic substrate, characterized in that: The raw materials for preparing the electroplating solution at least include 180 g / L - 250 g / L of copper sulfate pentahydrate, 50 g / L - 120 g / L of sulfuric acid, 50 mg / L - 80 mg / L of hydrochloric acid, as well as the first type of additive, the second type of additive, and the third type of additive; The first type of additive is a non-ionic surfactant, at least including one or several mixtures of polyethylene glycol, polypropylene glycol, sorbitan ester, polysorbate, or block copolymer. The concentration of the first type of additive in the electroplating solution is 300 mg / L - 500 mg / L; The second type of additive is a sulfonate anionic surfactant; the concentration of the second type of additive in the electroplating solution is 10 mg / L - 30 mg / L; The third type of additive is selected to be able to adjust the crystal grain structure of the electroplated copper during electroplating, play a polarization role in the electrodeposition process, so that the electroplating rate at the micro-peaks on the material surface is less than that at the micro-valleys for small molecule or polymer molecules of dyes or organic amines.

2. The electroplating solution for thick copper electroplating on a ceramic substrate according to claim 1, wherein, The sulfonate anionic surfactant at least includes one or several mixtures of sodium polydithiopropane sulfonate, sodium dodecylbenzenesulfonate, 3-mercapto-1-propanesulfonic acid sodium salt, and phenyl polydithiopropane sulfonate.

3. The electroplating solution for thick copper electroplating on a ceramic substrate according to claim 1, wherein The third type of additive is one or several of nitro blue tetrazolium chloride, thiazolyl blue, and acridine yellow.

4. The electroplating solution for thick copper electroplating on a ceramic substrate according to claim 3, characterized in that, The third type of additive uses thiazolyl blue and acridine yellow in combination.

5. The electroplating solution for thick copper electroplating on a ceramic substrate according to claim 4, wherein, The dosage of thiazolyl blue and acridine yellow in the electroplating solution is 1:0.1 - 0.

5.

6. The electroplating solution for thick copper electroplating on a ceramic substrate according to claim 3, characterized in that, The concentration of the third type of additive in the electroplating solution is 1 mg / L - 10 mg / L.

7. The electroplating solution for thick copper electroplating of a ceramic substrate according to claim 6, wherein, The concentration of the third type of additive in the electroplating solution is 3 mg / L - 8 mg / L.

8. The electroplating solution for thick copper electroplating on a ceramic substrate according to claim 1, characterized in that, The ceramic substrate is an aluminum nitride ceramic substrate.

9. A method for using the electroplating solution according to claim 1, characterized in that, At least include the following steps: S1. Degrease, micro-etch, and pre-dip the ceramic substrate; S2. Pour the prepared plating solution into the plating bath, use the ceramic substrate treated in S1 as the cathode, use soluble phosphor copper as the anode, and perform electroplating with a DC power supply. Among them, the current density is 0.5 A / dm 2 ~2 A / dm 2 , the temperature of the plating solution is 22 ± 3 °C, and the electroplating time is 400 - 900 min.

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